FSCTxxA-UH5

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Two components should be used to improve the heat exchange between the FSCT die and the heat sink,

that the temperature has to be monitored. These components are:

s

A thermal interface pad, in order to reduce the impact of air voids on the thermal impedance and to en-

sure an electrical insulation (if needed)

s

A clip to push the IPPAK against the heat sink and then to reduce also the interface thermal imped-

ance.

Several clips can be used depending on the heat sink type:

s

Saddle clips (cf.

figure 9) for slim heat sink;

s

U-clips (cf.

figure 10) for thick heat sink

s

Dedicated clips for special shape heat sink.

Fig. 9: IPPAK mounted with a Saddle clip.

Fig. 10: IPPAK mounted with a U-clip.

It can be noticed that the thickness of the IPPAK package (2.3 +/- 0.1 mm) is similar to those of SOT-32 and

SOT-82 (2.55 +/- 0.15 mm). The same clips can so be used for all these packages.

3.3 Temperature measurement error

Firstly, the time constant between a temperature variation on the external side on the IPPAK copper tab,

and the silicon die is in the range of a few hundred of milliseconds. As temperature phenomena are ex-

tremely slow for the targeted applications (the temperature of a MOSFET heat sink, increases typically with

an 1°C per second rate, in a power supply), the FSCT is able to react immediately to over-heating events.

Moreover, the very low junction to case thermal resistance (3 °C/W) reduces as much as possible the tem-

perature measurement error.

We calculate, in the following, this error considering both the package and the heatsink-Tab interface ther-

mal resistances (

figure 11).

Interface

Interface

Fig. 11: IPPAK Heatsink Interface.

Several companies offer adhesive and isolating

materials to be used as interface between elec-

tronic devices and a heat sink. These interfaces

can be provided with a shape dedicated for the

Tab foot print. For the IPPAK package, users could

choose a shape dedicated for SOT-32, SOT-82 or

even TO-126 or TO-220 packages (the more can

do the less).